Scalable OSPF configuration for managing optical networks

ABSTRACT

Systems and methods include receiving Open Shortest Path First (OSPF) packets from a plurality of OSPF areas; sending self-generated OSPF packets to the plurality of OSPF areas; and filtering of the received OSPF packets such that received Link State Advertisement (LSA) packets from an OSPF area (are not forwarded to other OSPF areas. In an embodiment, the systems and methods can be used for a scalable OSPF deployment for management of a network, such as an optical network.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present disclosure is a continuation of U.S. patent application Ser.No. 16/899,658, filed Jun. 12, 2020, the contents of which areincorporated by reference in their entirety.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to networking. Moreparticularly, the present disclosure relates to systems and methods fora scalable Open Shortest Path First (OSPF) configuration for managingoptical networks.

BACKGROUND OF THE DISCLOSURE

Open Shortest Path First (OSPF) is a routing protocol for InternetProtocol (IP) networks that uses a Link State Routing (LSR) algorithmand falls into the group of Interior Gateway Protocols (IGPs), operatingwithin a single Autonomous System (AS). OSPF is defined, for example, inRFC 2328 (1998) and RFC 5340 (2008), the contents of which areincorporated herein in their entirety. Also, network elements such as inan optical network are configured to communicate on a Data CommunicationNetwork (DCN) for Operations, Administration, Maintenance, andProvisioning (OAM&P) functions. Network operators would like to manageand deploy their optical networks in a cookie-cutter and scalablemanner. They would like to use an IGP such as Open Shortest Path First(OSPF) or Intermediate System to Intermediate System (ISIS) to allowcommunications between the network elements (i.e., logical East-Westcommunications) while using Border Gateway Protocol (BGP) to manage thecommunications between Network Management Systems (NMSs) and the networkelements (i.e., logical North-South communications).

One problem of using the IGP protocols to extend optical networks isthat network elements must maintain a small-sized network for simplemanagement or adopt complex network policies to extend the network to alarge scale. For example, one can configure the OSPF protocol with asingle OSPF area on small networks (e.g., ten or so network elements),or can scale to a large network by breaking the network into many smallOSPF autonomous systems and manage the interaction of the OSPFautonomous systems through other routing protocols.

BRIEF SUMMARY OF THE DISCLOSURE

The present disclosure relates to systems and methods for a scalableOpen Shortest Path First (OSPF) configuration for managing opticalnetworks. The scalable OSPF configuration is meant for simple, scalable,redundant, and applicable optical network deployment. By simple, thereis no need to manage the OSPF area assignment. By scalable, the OSPFnetwork can grow easily. By redundant, all network elements can haveredundant access to a Data Communication Network (DCN). By applicable,the deployment is designed for supporting Reconfigurable OpticalAdd/Drop Multiplexer (ROADMs) sites with a single network element havingpossible multiple degrees, multiple chassis, multiple shelves, etc. Thedescription herein references OSPF, but those skilled in the art willrecognize the same approach applies to ISIS networks. Central to theapproach described herein is the concept of an OSPF terminator that is aspecial kind of OSPF Link State Advertisement (LSA) filtering techniqueof ab OSPF router, which receives OSPF LSAs from an OSPF neighbor butdoes not flood the received OSPF LSAs to the other OSPF neighbors. Withthe approach described herein, it is possible to build a scalableoptical network in terms of management plane connectivity.

In an embodiment, a non-transitory computer-readable medium includesinstructions stored thereon for programming one or more processors, in anetwork element configured to operate in an optical network, to performsteps of causing communication to a router connected to a datacommunication network, for North-South communication; causingcommunication to a management plane associated with the optical networkvia one or more interfaces that are each connected to one or more OpenShortest Path First (OSPF) domains, for East-West communication; andimplementing an OSPF terminator between the one or more OSPF domainsthat includes receiving OSPF packets, sending self-generated OSPFpackets, and preventing flooding of received OSPF packets, between theone or more OSPF domains. The one or more OSPF domains can each have anarbitrarily selected OSPF area identifier, including where two of theOSPF domains have a same OSPF area identifier.

The OSPF terminator can include, for Database Description (DD) packets,only sending self-generated Link State Advertisements (LSAs). Thepreventing flooding of the received OSPF packets can include preventingthe flooding except for Link State Advertisements (LSAs) that need to beflooded back out a receiving interface. The North-South communicationcan be via Border Gateway Protocol (BGP) for communication to a NetworkManagement System (NMS). The East-West communication can be via any ofan Optical Service Channel (OSC), the data communications network, andvia an Internal Local Area Network (ILAN) interface associated with thenetwork element. The network element can be a Reconfigurable OpticalAdd/Drop Multiplexer (ROADM). The one or more OSPF domains can include alocal domain at a site where the ROADM is configured and a domain on anOptical Multiplex Section (OMS) connected to a degree associated withthe ROADM, and wherein a network element on the local domain isunreachable to another network element on the domain on the OMS. EveryROADM in the optical network can be configured to implement the OSPFterminator.

In another embodiment, a network element configured to operate in anoptical network includes a controller configured to connect to a routerconnected to a data communication network, for North-Southcommunication; optical line components configured to connect to theoptical network and to provide a management plane associated with theoptical network via one or more interfaces that are each connected toone or more Open Shortest Path First (OSPF) domains, for East-Westcommunication; and an OSPF terminator configured between the one or moreOSPF domains, wherein the OSPF terminator is configured to receive OSPFpackets, send self-generated OSPF packets, and prevent flooding ofreceived OSPF packets, between the one or more OSPF domains. The one ormore OSPF domains can each have an arbitrarily selected OSPF areaidentifier, including where two of the OSPF domains have a same OSPFarea identifier.

The OSPF terminator can be configured, for Database Description (DD)packets, to only send self-generated Link State Advertisements (LSAs),and the received OSPF packets are not flooded except for Link StateAdvertisements (LSAs) that need to be flooded back out a receivinginterface. The North-South communication can be via Border GatewayProtocol (BGP) for communication to a Network Management System (NMS).The East-West communication can be via any of an Optical Service Channel(OSC), the data communications network, and via an Internal Local AreaNetwork (ILAN) interface associated with the network element.

In a further embodiment, a method, implemented in a network elementconfigured to operate in an optical network includes causingcommunication to a router connected to a data communication network, forNorth-South communication; causing communication to a management planeassociated with the optical network via one or more interfaces that areeach connected to one or more Open Shortest Path First (OSPF) domains,for East-West communication; and implementing an OSPF terminator betweenthe one or more OSPF domains that includes receiving OSPF packets,sending self-generated OSPF packets, and preventing flooding of receivedOSPF packets, between the one or more OSPF domains. The one or more OSPFdomains can each have an arbitrarily selected OSPF area identifier,including where two of the OSPF domains have a same OSPF areaidentifier.

The OSPF terminator can include, for Database Description (DD) packets,only sending self-generated Link State Advertisements (LSAs), and thepreventing flooding of the received OSPF packets includes preventing theflooding except for Link State Advertisements (LSAs) that need to beflooded back out a receiving interface. The North-South communicationcan be via Border Gateway Protocol (BGP) for communication to a NetworkManagement System (NMS). The East-West communication can be via any ofan Optical Service Channel (OSC), the data communications network, andvia an Internal Local Area Network (ILAN) interface associated with thenetwork element. The network element can be a Reconfigurable OpticalAdd/Drop Multiplexer (ROADM).

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is illustrated and described herein withreference to the various drawings, in which like reference numbers areused to denote like system components/method steps, as appropriate, andin which:

FIG. 1 is a network diagram of a typical optical network deployment interms of a management plane;

FIG. 2 is a network diagram of an example optical network forillustrating communication requirements in the East-West managementplane;

FIG. 3 is a network diagram of the optical network of FIG. 2 withmultiple non-backbone OSPF areas in a non-backbone OSPF network;

FIG. 4 is a network diagram of the optical network of FIG. 2 with asingle OSPF area but one direction per ROADM network element;

FIG. 5 is a network diagram of the optical network of FIG. 2 withmultiple OSPF routing instances;

FIG. 6 is a network diagram of the optical network of FIG. 2 with anOSPF filter to control the LSA database;

FIG. 7 is a block diagram of the functionality of an OSPF terminator;

FIG. 8 is a network diagram of the optical network of FIG. 2 with OSPFterminators used therein for a simple, scalable, redundant, andapplicable approach to managing the optical network of FIG. 2;

FIG. 9 is a network diagram of an optical network with OSPF terminatorsused therein illustrating example operations;

FIG. 10 is a block diagram of an example network element for use withthe scalable OSPF systems and methods described herein;

FIG. 11 is a block diagram of a controller that can connect to a routerand implement the OSPF terminator of FIG. 7; and

FIG. 12 is a flowchart of a scalable Open Shortest Path First (OSPF)process, implemented in a network element configured to operate in anoptical network.

DETAILED DESCRIPTION OF THE DISCLOSURE

The present disclosure relates to systems and methods for a scalableOpen Shortest Path First (OSPF) configuration for managing opticalnetworks. The scalable OSPF configuration is meant for simple, scalable,redundant, and applicable optical network deployment. By simple, thereis no need to manage the OSPF area assignment. By scalable, the OSPFnetwork can grow easily. By redundant, all network elements can haveredundant access to a Data Communication Network (DCN). By applicable,the deployment is designed for supporting Reconfigurable OpticalAdd/Drop Multiplexer (ROADMs) sites with a single network element havingpossible multiple degrees, multiple chassis, multiple shelves, etc. Thedescription herein references OSPF, but those skilled in the art willrecognize the same approach applies to ISIS networks. Central to theapproach described herein is the concept of an OSPF terminator that is aspecial kind of OSPF LSA filtering technique of an OSPF router whichreceives OSPF LSAs from an OSPF neighbor but does not flood the receivedOSPF LSAs to the other OSPF neighbors. With the approach describedherein, it is possible to build a scalable optical network in terms ofmanagement plane connectivity.

Optical Network Management Plane

FIG. 1 is a network diagram of a typical optical network 10 deploymentin terms of a management plane. The optical network 10 includes networkelements 12 that are interconnected to one another optically. Thenetwork elements 12 can be Reconfigurable Optical Add/Drop Multiplexer(ROADMs) nodes, Optical Add/Drop Multiplexer (OADM) nodes, WavelengthDivision Multiplexed (WDM) nodes, or the like. That is, the networkelements 12 are terminal nodes. The physical hardware implementation ofthe network elements 12 can be chassis with modules, pizza-boxes (i.e.,integrated rack mounted units), etc. There is an East-West managementplane 14 between the network elements 12. This can include control planesignaling, OAM&P signaling, Optical Transport Network (OTN) signaling,etc. For example, the East-West management plane 14 can be through anin-band signaling mechanism such as the General Communication Channels(GCC) defined by ITU-T G.709 used to carry transmission management andsignaling information within OTN elements. Also, the East-Westmanagement plane 14 can utilize an Optical Service Channel (OSC) that isconfigured between the network elements 12 and which terminates atintermediate line amplifier network elements. Note, for illustrationpurposes, FIG. 1 does not illustrate any intermediate line amplifiernetwork elements between the network elements 12. Again, the East-Westmanagement plane 14 can use an IGP such as OSPF or ISIS forcommunication between the network elements 12.

The network elements 12 are each connected to a data communicationnetwork 16, such as via BGP and connections to routers 18. Note, thenetwork elements 12, being OADM, ROADM, etc. sites, are terminallocations, i.e., not remote huts for line amplifier network elements. Assuch, each network element 12 has data connectivity to the datacommunication network 16. The network elements 12 communicate to an NMS20 via the data communication network 16. Optionally, the networkelements 12 can also communicate with a Software-Defined Networking(SDN) controller 22 as well. The network elements 12 use BGP to managethe North-South communication to the data communication network 16.Those skilled in the art recognize the terms East-West and North-Southare used logically to describe management communications in a logicalsense.

Of note, a practical implementation of the optical network 10 could havehundreds or even thousands of network elements, including both thenetwork elements 12 and the line amplifier network elements. As such,the management configuration of the East-West management plane 14 iscritical and complex.

FIG. 2 is a network diagram of an example optical network 10A forillustrating communication requirements in the East-West managementplane 14. In this example network, the optical network 10A includes sixnetwork elements NE1, NE2, NE3, NE4, NE5, NE6 and two example ROADMsites 30A, 30B. The network element NE2 is a ROADM network element 12 atthe ROADM site 30A, and the network elements NE4, NE5 are ROADM networkelements 12 at the ROADM site 30B. The network elements NE1, NE3, NE6can be intermediate line amplifier network elements connected to theROADM sites 30A, 30B by fiber optic cables.

For the management plane 14, the optical network 10A includes the ROADMsites 30A, 30B and domains 32A, 32B, 32C. The domains 32A, 32B, 32Cextend from the ROADM sites 30A, 30B, and include the intermediate lineamplifier network elements. For example, a domain 32 can be an OpticalMultiplex Section (OMS), which is an all-optical section betweenOADM/ROADM sites 30A, 30B. The optical network 10A requires datacommunications between the network elements of a single site 30A, 30Band between the network elements of a single domain 32. For example, theNE2, NE3 and NE4 are required to communicate. The network elements NE4,NE5 are required to communicate. However, the network element NE3 doesnot need to communicate with the network element NE5. The communicationrequirement for the optical network 10A is that the network elementswithin a ROADM site are required to communicate and the network elementswithin a domain are required to communicate.

Of note, the optical network 10A has very few network elements forillustration purposes. Those skilled in the art recognize a practicalnetwork implementation can have tens, hundreds, or even thousands ofnetwork elements, tens, hundreds, or even thousands of domains 32, etc.

Conventional Management Plane Approaches

The following FIGS. 3-6 illustrate example approaches used today toscale the management plane 14 for the optical network 10. Namely FIG. 3is a network diagram of the optical network 10A with multiplenon-backbone OSPF areas in a non-backbone OSPF network. FIG. 4 is anetwork diagram of the optical network 10A with a single OSPF area butone direction per ROADM network element. FIG. 5 is a network diagram ofthe optical network 10A with multiple OSPF routing instances. FIG. 6 isa network diagram of the optical network 10A with an OSPF filter tocontrol the LSA database.

In FIG. 3, there is no OSPF backbone area configured in the opticalnetwork 10A, one unique non-backbone area 40A, 40B, 40D per domain, andone unique non-backbone area 40C per site. The loopback address of thenetwork elements that participate in multiple OSPF areas isredistributed to OSPF. The technique is to assign different OSPFnon-backbone area IDs to different routing domain (e.g., each area 40has a different OSPF area ID). Since the OSPF routes in one area cannotbe advertised to another due to the lack of backbone, an OSPF autonomoussystem can be divided into multiple routing domains.

Disadvantageously, the number of non-backbone areas will increase withnetwork growth, which causes difficulties in managing the OSPF area ID.The route redistribution will generate OSPF type-5 LSAs, the number ofwhich is proportional to the number of the OSPF areas. Therefore, theapproach cannot grow the optical network 10A infinitely. When theoptical network 10A becomes large, the overhead of managing the OSPFarea ID becomes a burden. Another problem is that the loopback IP of theROADM network elements can only be advertised to one OSPF area;therefore, the address must be redistributed to other OSPF areas. TheOSPF then generates type-3 LSAs, which has a global flooding scope.Therefore, the number of OSPF type-3 LSAs increases in terms of the sizeof the network, which prevents the optical network 10A from scaling.

In FIG. 4, a single OSPF area ID is used on each domain 32 with oneROADM network element managing one direction. There is OSPFcommunication with the sites 30A, 30B. However, the communication withinthe site 30B is provided by BGP. Since the OSPF routing information isisolated by BGP, each areas 40B, 40D in FIG. 4 become a separate OSPFautonomous system. Naturally, the network elements in the same OSPFautonomous system can communicate with each other. This approach cannotsupport a single ROADM network element per site, 30A. This approach isnot economical to deploy the optical network 10A because, in amulti-degree ROADM network element, each direction requires a separateROADM network element.

In FIG. 5, multiple OSPF instances are configured on the ROADM networkelement, one per optical direction. There is OSPF communication with thesites 30A, 30B. This approach configures multiple OSPF routing instanceson the ROADM network element, one for each direction. Since the routinginformation learned by each routing instance is isolated to that routinginstance, each area 40A, 40B, 40D in FIG. 5 becomes a separate OSPFautonomous system. Compared to the approach in FIG. 4, this approach cansupport a single ROADM network element per site 30A. This approachrequires putting multiple OSPF routing instances on a network elementwith multiple degrees, requiring careful network planning and consumingmore computation and memory resources.

In FIG. 6, OSPF filtering is used to filter out certain types of LSAs sothat the LSA database of the OSPF is reduced. Therefore, the system canhandle larger networks. The OSPF filtering is used to control the numberof LSAs flooding in the optical network 10A. The OSPF LSA filter can beused to determine which type of LSAs can be flooded or accepted on anetwork element. The OSPF route filter can be used to filter out the LSAassociated with a route. The OSPF area filter can be used to filter outroutes from a specified area. The OSPF filter is LSA type-based filter.For a large network, the route redistribution will generate asignificant volume of type-5 LSAs, which are hard to filter out. This isused to reduce the number of LSAs to achieve OSPF scalability. Oneproblem is that the existing OSPF filtering is based on LSA type but notthe topology. Therefore, a lot of irrelevant LSAs cannot be filteredout. For example, if a device requires one type-5 LSA for DCN access, itmust keep all type-5 LSAs. Hence, the ability to scale the opticalnetwork 10A is limited. If the users want to scale the optical network10A, they must define a set of filtering rules tailored to each device,which adds the network configuration complex and management cost.

Another approach is to use an OSPF stub area, and route summarization toreduce the number of LSAs to gain network scalability. OSPF stub area(RFC2328 and RFC3101) is an area in which only one OSPF routerconnecting to the standard OSPF area. The router can then issue thedefault route to the stub area shielding the external LSAs. Both totallystubby area and Not-So-Stubby Area (NSSA) follow the same rule above.The only difference is that the NSSA allows an external route to beredistributed into the stub area. The stub areas do not satisfycustomer's requirements because it needs to manage the OSPF areaassignment and cannot support redundancy. RFC3137 defines the behaviorthat a router can originate an LSA with the maximal metric so that theother routers avoid using the transit path via the router to forwardtraffic. The OSPF Stub Router Advertisement solution does not satisfycustomer's requirements because it can only be used to direct thetransit traffic, but it cannot reduce the number of LSAs within thenetwork. Therefore, the number of LSAs will increase in terms of thesize of networks.

OSPF Terminator

Again, the aforementioned approaches address some aspects ofscalability. However, there is still a need for a simple, scalable,redundant, and applicable approach. The present disclosure includes anOSPF terminator that implements a special type of OSPF LSA filteringthat receives OSPF LSAs from an OSPF neighbor but does not flood thereceived OSPF LSAs to the other OSPF neighbors. FIG. 7 is a blockdiagram of the functionality of an OSPF terminator 50. As noted in FIG.7, the OSPF terminator is configured to receive LSAs, to sendself-originating LSAs, but not to forward received LSAs. That is, theOSPF terminator 50 is a special OSPF router that can receive OSPFpackets, send self-generated OSPF packets, but never flood its receivedOSPF packets to its OSPF neighbors.

Specifically, the OSPF terminator 50 is based on the modification of theOSPF router behavior defined in RFC 2328. Relative to Section 7.2 of RFC2328, when the OSPF router attempts to send Database Description (DD)packets, only the self-originated LSAs are attached to the packet. As acomparison, the standard requires attachment of all the LSAs to the DDpackets. Next, this includes modification of the Bullet 5(b) of Section13 of the RFC 2328, namely the OSPF terminator 50 does not flood newlyreceived LSAs out any subnet of the router's interfaces, except for thecases the LSAs need to be flooded back out the receiving interface. As acomparison, the standard requires to flood the LSAs out some subnet ofthe router's interfaces.

FIG. 8 is a network diagram of the optical network 10A with OSPFterminators 50 used therein for a simple, scalable, redundant, andapplicable approach to managing the optical network 10A. The OSPFterminator 50 operates as described above. The configuration rules forthe OSPF terminators 50 in the optical network 10A are as follows. TheOSPF terminator 50 functionality is configured on all ROADM networkelements with degrees, namely the network elements NE2, NE4, NE5. Theoptical network 10A includes a single OSPF area ID across the entirenetwork. Here, the domains 40A, 40B, 40D all have the same OSPF area ID.Again, functionally, the OSPF traffic will be stopped at the OSPFterminator 50, and the LSA database is reduced. This leads to acookie-cutter approach—the same OSPF configuration can be replicated toeach site 30 and domain 32. The communication network, i.e., themanagement plane 14, can grow without limitation. Also, this approachsupports a single ROADM network element and multiple ROADM networkelement configurations.

FIG. 9 is a network diagram of an optical network 10B with OSPFterminators 50 used therein illustrating example operations. The opticalnetwork 10B includes four ROADM sites 30A, 30B, 30C, 30D. The ROADMsites 30A, 30D include a single ROADM network element NE1, NE8, aresingle degree sites, and the network elements NE1, NE8 connect to BGProuters 18A, 18D, respectively. The ROADM site 30B has a single ROADMnetwork element NE2, but it is a three-degree site, and the networkelement NE2 is connected to a BGP router 18B. Finally, the ROADM site30C has three ROADM network elements NE5, NE6, NE7, with eachinterconnected to one another. The network element NE5 is a two-degreeconfiguration, the network element NE6 is a single degree, and eachconnects to a BGP router 18C. For example, the network element NE7 can aAdd/Drop or pre-combiner network element without degrees. Theconnections between the network elements NE1, NE2, NE5, NE6, NE8 and BGProuters are Local Area Network (LAN) connections. Also, the opticalnetwork 10B includes two line amplifier network elements NE3, NE4between the network elements NE2, NE5. FIG. 9 is presented to illustratehow the OSPF terminators 50 can be used to realize a scalable OSPF-basedoptical network in a cookie-cutter manner.

The North-South communication channel is established by the BGPprotocol, while the East-West communication channel is established bythe OSPF protocol. Different from traditional OSPF networks describedherein; the East-West OSPF networks are operated on a single OSPF area.The area ID is arbitrarily chosen. The network elements within a ROADMsite can be connected via ILAN interfaces (the ROADM site 30C) or viaDCN routers (the ROADM site 30B). When a network element, such as thenetwork elements NE1, NE2, NE5, NE6, NE8, is a network element withdegrees which connects, via OSC interfaces, to another ROADM site 30,these network elements must connect to the DCN BGP router 18 and theOSPF terminator 50 has to be enabled. For example, at the ROADM site30C, the network elements NE5, NE6 must connect to the BGP router 18Cand have the OSPF terminator 50 enabled. Conversely, if a networkelement is not a network element with degrees and does not haveconnections to another ROADM site, no OSPF terminator 50 is required,e.g., the NE7 at the ROADM site 30C. Also, the network elements NE1,NE2, NE8 are configured with connections to the BGP routers 18A, 18B,18D, and with the OSPF terminators 50.

The OSPF terminator separates the single OSPF AS into six independentOSPF routing domains 32A-32F. The devices within the same OSPF routingdomain 32 have IP reachability, while those in different domains 32 donot. For example, the network elements NE2, NE3 and NE5 are connectedvia OSC interfaces and within the same routing domain 32B so they cancommunicate with each other. The network elements NE3, NE4 cannot reacheach other because they are in different domains 32B, 32C. The OSPFterminator 50 on the network elements NE2, NE5 prevents routes frombeing leaked between the domains 32.

The deployment method using the OSPF terminators satisfies the goalsoutlined herein—simple, scalable, redundant, and applicable. For simple,a network operator does not need to plan OSPF networks; an arbitraryOSPF area ID can be assigned to every network element (these can be thesame, different, it does not matter). Arbitrary means just that—it canbe any value. For scalable, the deployment can grow the optical network10 infinitely because the OSPF terminators 50 separate a big OSPFautonomous system into independent OSPF routing domains 32. No OSPFtraffic is leaked between these routing domains 32. Therefore, the sizeof the OSPF Link State (LS) database and IP routing table does not growin terms of the size of the optical network 10.

For redundant, each network element can be accessed by a Gateway NetworkElement (GNE) with the OSPF terminator 50 enabled. That is, every OADMnetwork element 12 with degrees is a GNE, connected to the router 18.For applicable, this deployment approach supports a ROADM site with asingle network element and a ROADM site with multiple network elements.

The OSPF terminator 50 satisfies all the network planning requirementsdescribed herein to make the user's network design simpler and scalable.The OSPF terminator 50 terminates the OSPF LSAs at the ROADM networkelement 12 so that the OSPF area planning is not necessary, and thenumber of LSAs in the optical network 10 is restricted between the OSPFterminators 50.

Since this approach does not change the OSPF LSA propagation between twoOSPF terminators 50, the network elements in between always haveredundant access (East and West), which satisfies the redundancyrequirement.

Since the OSPF terminator 50 terminates all OSPF LSAs, it does not leakLSAs from one area to another, even on a single network element.Therefore, a ROADM site with multiple degrees (directions), the LSAs areconstraint within that direction. So, the optical network 10 can scaleeven under this configuration.

Advantageously, the present disclosure does not require networkoperators to manage OSPF area ID, does not require multiple OSPFinstances, does not require additional IGP protocols, and the OSPFterminator 50 can filter out all irrelevant LSAs to gain high networkscalability. Thus, the present disclosure can be used to quickly andefficiently deploy the optical network 10 from the perspective of themanagement plane 14, in a cookie-cutter based network deployment.

Example Network Element/Node

FIG. 10 is a block diagram of an example network element 12 for use withthe scalable OSPF systems and methods described herein. In anembodiment, the network element 12 can be a device that may consolidatethe functionality of a Multi-Service Provisioning Platform (MSPP),Digital Cross-Connect (DCS), Ethernet and/or Optical Transport Network(OTN) switch, Wave Division Multiplexed (WDM)/DWDM platform, PacketOptical Transport System (POTS), etc. into a single, high-capacityintelligent switching system providing Layer 0, 1, 2, and/or 3consolidation. In another embodiment, the network element 12 can be anyof a WDM/DWDM terminal, an OADM, a ROADM, etc. That is, the networkelement 12 can be any digital and/or optical system with ingress andegress digital and/or optical signals and switching of channels,timeslots, tributary units, wavelengths, etc.

In an embodiment, the network element 200 includes common equipment 202,one or more line modules 204, and one or more switch modules 206. Thecommon equipment 202 can include power; a control module such as acontroller 300, as illustrated in FIG. 11; OAM&P access; user interfaceports; and the like. The common equipment 202 can connect to themanagement plane 14 through the router 18. Additionally, the commonequipment 202 can include a controller, a shelf processor, a controlplane processor, etc. such as a controller 300 illustrated in FIG. 3.The network element 12 can include an interface 212 for communicativelycoupling the common equipment 202, the line modules 204, and the switchmodules 206 to one another. For example, the interface 212 can be abackplane, midplane, a bus, optical and/or electrical connectors, or thelike. The line modules 204 are configured to provide ingress and egressto the switch modules 206 and to external connections on the linksto/from the network element 12. In an embodiment, the line modules 204can form ingress and egress switches with the switch modules 206 ascenter stage switches for a three-stage switch, e.g., a three-stage Closswitch. Other configurations and/or architectures are also contemplated.

Further, the line modules 204 can include a plurality of opticalconnections per module, and each module may include a flexible ratesupport for any type of connection. The line modules 204 can include WDMinterfaces, short-reach interfaces, pluggable modules, and the like, andcan connect to other line modules 204 on remote network elements, endclients, edge routers, and the like, e.g., forming connections on thelinks in the optical network 10. From a logical perspective, the linemodules 204 provide ingress and egress ports to the network element 12,and each line module 204 can include one or more physical ports. Theswitch modules 206 are configured to switch channels, timeslots,tributary units, packets, etc. between the line modules 204. Forexample, the switch modules 206 can provide wavelength granularity(Layer 0 switching); OTN granularity; Ethernet granularity; and thelike.

The network element 12 can include a chassis (shelf) where the equipment202 and the modules 204, 206 are realized as cards, modules, circuitpacks, blades, etc. As described herein, the term module is used torepresent all of these hardware devices. Here, a module is physicallyinserted in the chassis and connected to the interface 212. The networkelement 12 is illustrated with the line modules 204 and the switchmodules, as well as the controller 300. Other types of modules are alsocontemplated. Further, there can be a variety of different types of linemodules 204 and switch modules 206.

Also, those of ordinary skill in the art will recognize the networkelement 12 can include other components which are omitted forillustration purposes, and that the systems and methods described hereinare contemplated for use with a plurality of different network elementswith the network element 12 presented as an example type of networkelement. For example, in another embodiment, the network element 12 maynot include the switch modules 206, but rather have the correspondingfunctionality in the line modules 204 (or some equivalent) in adistributed fashion. Also, the network element 12 may omit the switchmodules 206 and that functionality, such as in a WDM network element,ROADM, OADM, etc. For the network element 12, other architecturesproviding ingress, egress, and switching are also contemplated for thesystems and methods described herein. In a further embodiment, thechassis and modules may be a single integrated unit, namely arack-mounted shelf where the functionality of the modules 204, 206 isbuilt-in, i.e., a “pizza-box” configuration.

Note, the network element can be configured as a single “shelf” ormultiple “shelves.” Those of ordinary skill in the art will recognizethe term shelf can refer to a chassis, a rack-mounted unit (pizza box),etc. A network element, i.e., a node, is a single entity from a networkmanagement, OAM&P, etc. perspective. Here, a network element may includeone or more shelves, with each shelf having its own controller 300.

Example Controller

FIG. 11 is a block diagram of a controller 300, which can connect to therouter 18 and implement the OSPF terminator 50 described herein. Thecontroller 300 can be part of the common equipment, such as commonequipment 202 in the network element 12, or a stand-alone devicecommunicatively coupled to the network element 12 via the datacommunication network 16. Further, the controller 300 can be referred toin implementations as a control module, a shelf controller, a shelfprocessor, a system controller, etc. As described herein, the controller300 is meant to cover any processing device that is used to control theoperation of a network element 12, including connectivity to the router18 for the management plane 14. Specifically, the controller 300 canimplement the OSPF terminator 50 described herein. The controller 300can include a processor 302, which is a hardware device for executingsoftware instructions. The processor 302 can be any custom made orcommercially available processor, a central processing unit (CPU), anauxiliary processor among several processors associated with thecontroller 300, a semiconductor-based microprocessor (in the form of amicrochip or chipset), or generally any device for executing softwareinstructions. When the controller 300 is in operation, the processor 302is configured to execute software stored within the memory, tocommunicate data to and from the memory, and to generally controloperations of the controller 300 pursuant to the software instructions.The controller 300 can also include a network interface 304, a datastore 306, memory 308, an I/O interface 310, and the like, all of whichare communicatively coupled to one another and to the processor 302.

The network interface 304 can be used to enable the controller 300 tocommunicate with the router 18 in the data communication network 16,such as to communicate North-South as to the NMS 20, to the SDNcontroller 22, and the like. Further, the common equipment 202 may alsoinclude an OSC module for East-West communication, and the line modules204 can also provide East-West communication such as via overhead. Thenetwork interface 304 can include, for example, an Ethernet module. Thenetwork interface 304 can include address, control, and/or dataconnections to enable appropriate communications on the network. Thedata store 306 can be used to store data, such as control planeinformation, provisioning data, OAM&P data, etc. The data store 306 caninclude any of volatile memory elements (e.g., random access memory(RAM, such as DRAM, SRAM, SDRAM, and the like)), nonvolatile memoryelements (e.g., ROM, hard drive, flash drive, CDROM, and the like), andcombinations thereof. Moreover, the data store 306 can incorporateelectronic, magnetic, optical, and/or other types of storage media. Thememory 308 can include any of volatile memory elements (e.g., randomaccess memory (RAM, such as DRAM, SRAM, SDRAM, etc.)), nonvolatilememory elements (e.g., ROM, hard drive, flash drive, CDROM, etc.), andcombinations thereof. Moreover, the memory 308 may incorporateelectronic, magnetic, optical, and/or other types of storage media. Notethat the memory 308 can have a distributed architecture, where variouscomponents are situated remotely from one another, but may be accessedby the processor 302. The I/O interface 310 includes components for thecontroller 300 to communicate with other devices. Further, the I/Ointerface 310 includes components for the controller 300 to communicatewith the other nodes, such as using overhead associated with OTNsignals, an Optical Service Channel (OSC), etc.

Again, the network element 12 performs North-South communication withthe router 18 to the data communication network 16. This functionalitymay be performed by the network interface 304. The network element 12also performs East-West communication with other network elements viathe management plane 14. This functionality may be performed by thecontroller 300, by the common equipment 202, such as an OSC module, bythe line modules 204, such as via overhead, by the network interface304, etc. The OSPF terminator 50 functionality is provided for theEast-West communication. Thus, the OSPF terminator 50 functionality maybe performed by any of the controller 300, the common equipment 202 suchas an OSC module, by the line modules 204, such as via overhead, by thenetwork interface 304, etc., individually or in combination with oneanother. That is, the present disclosure is presenting the networkelement 12 in FIG. 10 and the controller 300 in FIG. 11 for illustrationpurposes. Those skilled in the art will recognize various physicalimplementations are possible and contemplated herein for the East-Westcommunication in the management plane 14.

Scalable OSPF Process

FIG. 12 is a flowchart of a scalable Open Shortest Path First (OSPF)process 400, implemented in a network element 12 configured to operatein the optical network 10. The process 400 can be a computer-implementedmethod, embodied in a non-transitory computer-readable medium havinginstructions stored thereon for programming one or more processors, andimplemented in the network element 12.

The scalable OSPF process 400 includes causing communication to a routerconnected to a data communication network, for North-South communication(step 402); causing communication to a management plane associated withthe optical network via one or more interfaces that are each connectedto one or more Open Shortest Path First (OSPF) domains, for East-Westcommunication (step 404); and implementing an OSPF terminator betweenthe one or more OSPF domains that includes receiving OSPF packets,sending self-generated OSPF packets, and preventing flooding of receivedOSPF packets, between the one or more OSPF domains (step 406).

The one or more OSPF domains can each have an arbitrarily selected OSPFarea identifier, including where two of the OSPF domains have a sameOSPF area identifier. That is, the same OSPF area identifier can be usedin every domain. Also, it could be a random value. The key point isthere is no need to manage separate domains because of the OSPFterminator.

The OSPF terminator can include, for Database Description (DD) packets,only sending self-generated Link State Advertisements (LSAs). Thepreventing flooding of the received OSPF packets can include preventingthe flooding except for Link State Advertisements (LSAs) that need to beflooded back out a receiving interface.

The North-South communication can be via Border Gateway Protocol (BGP)for communication to a Network Management System (NMS). The East-Westcommunication can be via any of an Optical Service Channel (OSC), thedata communications network, and via an Internal Local Area Network(ILAN) interface associated with the network element.

The network element can be a Reconfigurable Optical Add/Drop Multiplexer(ROADM). The one or more OSPF domains can include a local domain at asite where the ROADM is configured, and a domain on an Optical MultiplexSection (OMS) connected to a degree associated with the ROADM, andwherein a network element on the local domain is unreachable to anothernetwork element on the domain on the OMS. Every ROADM in the opticalnetwork is configured to implement the OSPF terminator.

In another embodiment, a network element configured to operate in anoptical network includes a controller configured to connect to a routerconnected to a data communication network, for North-Southcommunication; optical line components configured to connect to theoptical network and to provide a management plane associated with theoptical network via one or more interfaces that are each connected toone or more Open Shortest Path First (OSPF) domains, for East-Westcommunication; and an OSPF terminator configured between the one or moreOSPF domains that includes receiving OSPF packets, sendingself-generated OSPF packets, and preventing flooding of received OSPFpackets, between the one or more OSPF domains.

It will be appreciated that some embodiments described herein mayinclude or utilize one or more generic or specialized processors (“oneor more processors”) such as microprocessors; Central Processing Units(CPUs); Digital Signal Processors (DSPs): customized processors such asNetwork Processors (NPs) or Network Processing Units (NPUs), GraphicsProcessing Units (GPUs), or the like; Field-Programmable Gate Arrays(FPGAs); and the like along with unique stored program instructions(including both software and firmware) for control thereof to implement,in conjunction with certain non-processor circuits, some, most, or allof the functions of the methods and/or systems described herein.Alternatively, some or all functions may be implemented by a statemachine that has no stored program instructions, or in one or moreApplication-Specific Integrated Circuits (ASICs), in which each functionor some combinations of certain of the functions are implemented ascustom logic or circuitry. Of course, a combination of theaforementioned approaches may be used. For some of the embodimentsdescribed herein, a corresponding device in hardware and optionally withsoftware, firmware, and a combination thereof can be referred to as“circuitry configured to,” “logic configured to,” etc. perform a set ofoperations, steps, methods, processes, algorithms, functions,techniques, etc. on digital and/or analog signals as described hereinfor the various embodiments.

Moreover, some embodiments may include a non-transitorycomputer-readable medium having instructions stored thereon forprogramming a computer, server, appliance, device, one or moreprocessors, circuit, etc. to perform functions as described and claimedherein. Examples of such non-transitory computer-readable mediuminclude, but are not limited to, a hard disk, an optical storage device,a magnetic storage device, a Read-Only Memory (ROM), a Programmable ROM(PROM), an Erasable PROM (EPROM), an Electrically EPROM (EEPROM), Flashmemory, and the like. When stored in the non-transitorycomputer-readable medium, software can include instructions executableby a processor or device (e.g., any type of programmable circuitry orlogic) that, in response to such execution, cause a processor or thedevice to perform a set of operations, steps, methods, processes,algorithms, functions, techniques, etc. as described herein for thevarious embodiments. Specifically, the OSPF terminator 50 describedherein can be implemented as instructions executable by a processor ordevice, as a processor or device configured to perform the associatedsteps, as a circuit including software and/or firmware, and the like.

Although the present disclosure has been illustrated and describedherein with reference to preferred embodiments and specific examplesthereof, it will be readily apparent to those of ordinary skill in theart that other embodiments and examples may perform similar functionsand/or achieve like results. All such equivalent embodiments andexamples are within the spirit and scope of the present disclosure, arecontemplated thereby, and are intended to be covered by the followingclaims.

What is claimed is:
 1. A non-transitory computer-readable mediumcomprising instructions which, when executed on at least one processor,cause the at least one processor to carry the steps of: receiving OpenShortest Path First (OSPF) packets from a plurality of OSPF areas;sending self-generated OSPF packets to the plurality of OSPF areas; andfiltering of the received OSPF packets such that received Link StateAdvertisement (LSA) packets from an OSPF area are not forwarded to otherOSPF areas.
 2. The non-transitory computer-readable medium of claim 1,wherein the plurality of OSPF areas each have an arbitrarily selectedOSPF area identifier, including where two of the OSPF areas have a sameOSPF area identifier.
 3. The non-transitory computer-readable medium ofclaim 1, wherein, for Database Description (DD) packets, onlyself-generated LSAs are attached thereto.
 4. The non-transitorycomputer-readable medium of claim 1, wherein the filtering includespreventing flooding except for LSA packets that need to be flooded backout a receiving interface.
 5. The non-transitory computer-readablemedium of claim 1, wherein the steps include communicating to a routerconnected to a data communication network; and communicating to amanagement plane via a plurality of interfaces each connected to anassociated area of the plurality of OSPF areas.
 6. The non-transitorycomputer-readable medium of claim 5, wherein the management plane isassociated with a network that includes a plurality of network elements.7. The non-transitory computer-readable medium of claim 5, wherein thecommunicating to the router is via Border Gateway Protocol (BGP) forcommunication to a Network Management System (NMS).
 8. Thenon-transitory computer-readable medium of claim 5, wherein thecommunicating to the management plane is via any of an Optical ServiceChannel (OSC), the data communications network, and via an InternalLocal Area Network (ILAN) interface associated with the network element.9. The non-transitory computer-readable medium of claim 5, wherein thenetwork element is a Reconfigurable Optical Add/Drop Multiplexer(ROADM).
 10. The non-transitory computer-readable medium of claim 9,wherein the plurality of OSPF areas include a local domain at a sitewhere the ROADM is configured and a domain on an Optical MultiplexSection (OMS) connected to a degree associated with the ROADM, andwherein a network element on the local domain is unreachable to anothernetwork element on the domain on the OMS.
 11. A controller comprising:at least one processor and memory comprising instructions, when executedon the at least one processor, cause the at least one processor toreceive Open Shortest Path First (OSPF) packets from a plurality of OSPFareas, send self-generated OSPF packets to the plurality of OSPF areas,and filter the received OSPF packets such that received Link StateAdvertisement (LSA) packets from an OSPF area are not forwarded to otherOSPF areas.
 12. The controller of claim 11, wherein the plurality ofOSPF areas each have an arbitrarily selected OSPF area identifier,including where two of the OSPF areas have a same OSPF area identifier.13. The controller of claim 11, wherein, for Database Description (DD)packets, only self-generated LSAs are attached thereto.
 14. Thecontroller of claim 11, wherein the filtering includes preventingflooding except for LSA packets that need to be flooded back out areceiving interface.
 15. The controller of claim 11, wherein theinstructions further cause the at least one processor to communicate toa router connected to a data communication network, and communicate to amanagement plane via a plurality of interfaces each connected to anassociated area of the plurality of OSPF areas.
 16. A method comprising:receiving Open Shortest Path First (OSPF) packets from a plurality ofOSPF areas; sending self-generated OSPF packets to the plurality of OSPFareas; and filtering of the received OSPF packets such that receivedLink State Advertisement (LSA) packets from an OSPF area are notforwarded to other OSPF areas.
 17. The method of claim 16, wherein theplurality of OSPF areas each have an arbitrarily selected OSPF areaidentifier, including where two of the OSPF areas have a same OSPF areaidentifier.
 18. The method of claim 16, wherein, for DatabaseDescription (DD) packets, only self-generated LSAs are attached thereto.19. The method of claim 16, wherein the filtering includes preventingflooding except for LSA packets that need to be flooded back out areceiving interface.
 20. The method of claim 16, further comprisingcommunicating to a router connected to a data communication network; andcommunicating to a management plane via a plurality of interfaces eachconnected to an associated area of the plurality of OSPF areas.